This research program involves three interrelated and interacting projects that will use novel approaches to elucidate regulatory mechanisms in acute myocardial ischemia, injury, repair, and heart failure that have relevance to human cardiac disease. The overall proposal will make extensive use of transgenic and gene targeted deletion models in mice. Methods will include biochemical and molecular approaches in isolated submitochondrial particles and intact mitochondria; biochemical and molecular studies in cell culture; biophysical studies in isolated cells and myocardial strips; hemodynamic investigations in isolated hearts; and serial hemodynamic and echocardiographic studies in living animals. All of the required techniques are currently in use in the laboratories of the responsible investigators. Cellular and molecular processes not previously investigated in the heart will be targeted. The first overall goal is to learn about how the lysophospholipid mediators sphingosine I -phosphate and lysophosphatidic acid and the actin regulatory protein gelsolin regulate myocardial responses to acute oxidative stress, injury, and remodeling. The second aim is to study the molecular regulation of matrix metalloproteinase-2 (gelatinase A) in cardiac fibroblast proliferation, extracellular matrix formation, and cardiac remodeling. The third aim is to learn how calcium responsiveness is regulated in models of acute myocardial ischernia and reversible congestive heart failure. These projects will rely on three Core Units: a hemodynamics core, a cell culture core, and a transgenic mouse core. Each of the projects will have extensive interactions with the other projects and with the core units. This proposal brings together the skills of a diverse group of investigators united by an interest in understanding mechanisms underlying the heart's response to oxidative stress. The proposed studies are novel and feasible, and are designed to lead to new approaches for the prevention of myocardial damage during acute and chronic oxidative stress.